MV-mimicking micelles loaded with PEG-serine-ACP nanoparticles to achieve biomimetic intra/extra fibrillar mineralization of collagen in vitro

Since their discovery, matrix vesicles (MVs) containing minerals have received considerable attention for their role in the mineralization of bone, dentin and calcified cartilage. Additionally, MVs' association with collagen fibrils, which serve as the scaffold for calcification in the organic matrix, has been repeatedly highlighted. The primary purpose of the present study was to establish a MVs–mimicking model (PEG-S-ACP/micelle) in vitro for studying the exact mechanism of MVs-mediated extra/intra fibrillar mineralization of collagen in vivo. In this study, high-concentration serine was used to stabilize the amorphous calcium phosphate (S-ACP), which was subsequently mixed with polyethylene glycol (PEG) to form PEG-S-ACP nanoparticles. The nanoparticles were loaded in the polysorbate 80 micelle through a micelle self-assembly process in an aqueous environment. This MVs–mimicking model is referred to as the PEG-S-ACP/micelle model. By adjusting the pH and surface tension of the PEG-S-ACP/micelle, two forms of minerals (crystalline mineral nodules and ACP nanoparticles) were released to achieve the extrafibrillar and intrafibrillar mineralization, respectively. This in vitro mineralization process reproduced the mineral nodules mediating in vivo extrafibrillar mineralization and provided key insights into a possible mechanism of biomineralization by which in vivo intrafibrillar mineralization could be induced by ACP nanoparticles released from MVs. Also, the PEG-S-ACP/micelle model provides a promising methodology to prepare mineralized collagen scaffolds for repairing bone defects in bone tissue engineering.     

Influence of intertree distance on foraging behaviour of Rhagoletis pomonella in the field

Abstract. 1. We tested a prediction from contemporary foraging theory that animals should decrease their allocation of energy to the searching of individual patches when interpatch travel costs decrease.
2. We used individual Rhagoletis pomonella Walsh (Diptera: Tephritidae) females foraging for oviposition sites (= Crataegus fruit) in a host tree which was surrounded by four other trees at varying distances.
3. We found that flies generally invested less search, measured as time spent searching a tree or number of leaves visited on a tree, when neighbouring trees were nearby than when farther away.
4. Under our test conditions, flies appeared to have difficulty locating neighbouring trees at a distance of more than 1.6 m.
5. Our study calls into question the interpretation of search effort by insects within resource patches in the absence of information on interpatch distances.     

The role of context, colour and location cues in socially learned novel food source preferences in starlings, Sternus vulgaris

Although the opportunity for errors in social learning is widely recognised, as yet little research has been directed towards understanding specific inaccuracies, biases and limitations in social learning and the mechanisms that give rise to them. In two experiments I ask how starlings, Sternus vulgaris, identify exemplars of novel feeders previously learned about socially. I find that starlings have a stronger response to feeders in the same context as that in which social learning took place, compared to identical and nonidentical feeders in a different context. Within a context that matches where social learning took place, starlings prefer feeders that show the same location and colour as the feeder demonstrated by the demonstrator starling, and show no preference when colour and location cues are dissociated. This suggests that starlings are relatively accurate social learners, since they show strong responses to novel foraging options only if they match the context, colour and location of options learned about socially, and they do so after very few trials. Furthermore, the responses of the subjects were compatible with conditioned learning-like mechanisms, which provide a useful basis for the further investigation of the origins and implications of errors in social learning.     

“绿色革命”新进展:赤霉素与氮营养双重调控的表观修饰助力水稻高产高效育种

以半矮秆育种为代表的“绿色革命”极大地提高了作物产量,但也带来氮营养利用效率降低的严重问题。“绿色革命”主要基于调控赤霉素的代谢和信号转导而实现。前期的研究发现,赤霉素信号转导关键因子DELLA蛋白通过调控GRF4而负调控氮素的吸收利用,为半矮秆品系氮利用效率低的问题提供了解决方案。最近的一项研究进一步揭示了GA信号途径与氮响应交叉互作的新机制。该研究发现水稻(Oryza sativa)NGR5是氮素调控分蘖数目的一个关键基因,其表达受氮诱导。通过招募PRC2,NGR5对D14和OsSPL14等分蘖抑制基因所在位点进行H3K27me3甲基化修饰,从而抑制其表达。而在半矮秆背景下超表达NGR5可以提高低氮水平下的水稻产量。NGR5同时也被发现为赤霉素受体GID1的一个新靶标,受到其负调控。该研究发现了调控赤霉素信号通路的新机制,并对高产高效的新一代“绿色革命”育种实践具有重要启示。     

The cost of mutualism in a fly-fungus interaction

The movement ability of individuals has become increasingly important to a variety of ecological questions. In this study, I investigate how plant structure and changes in body size through development affect the movement ability of a predaceous stinkbug, Podisus maculiventris, on three species of goldenrod (Solidago spp.) representing a wide range of surface complexities. I adapt existing techniques for quantifying movement in two dimensions to the study of movement on natural plant structures in three dimensions. These experiments indicate that plant structure and insect size are significant factors affecting the movement ability of P. maculiventris. Changes in movement ability due to factors of ontogeny and different habitat structures suggest that the scale of an individual’s ambit or ecological sphere of influence may vary within its lifespan. Considering the influence of ontogeny and habitat structure on movement ability may be useful to investigations of population dynamics, foraging behavior, and pest management. Received: 14 July 1999 / Accepted: 23 March 2000     

Functional analysis of the C-terminal propeptide of keratinase from Bacillus licheniformis BBE11-1 and its effect on the production of keratinase in Bacillus subtilis

The keratinase from Bacillus licheniformis BBE11-1 is a serine protease and expressed as a pre-pro-precursor. To produce a mature and active keratinase, the propeptide must be cleaved on the C-terminal via cis or trans. In this study, to enhance the production of keratinase in Bacillus subtilis, single amino acid substitutions, single residue deletions and linkers were introduced at the C-terminus of the propeptide. The results showed that optimizing the residue of cleavage site of propeptide will affect the cleavage efficiency of propeptide, and the mature enzyme yield of Leu(P1)Ala mutant increases 50% compared with the wild-type. In addition, inserting linkers and deleting individual residues at the C-terminal of the propeptide decreases the mature keratinase production. Our results indicated that the primary structure of the C-terminus of propeptide is crucial for the mature keratinase production. Propeptide engineering at C-terminus may be an effective approach to increase the yield of keratinase.     

The Effect of Leaf Age on Gas Exchange and Malate Accumulation in C3-CAM Plant Marrubium Frivaldszkyanum (Lamiaceae)

For the first time the expression of C₃ and CAM in the leaves of different age of Marrubium frivaldszkyanum Boiss, is reported. With increasing leaf age a typical C₃ photosynthesis pattern and high transpiration rate were found. In older leaves a shift to CAM occurred and the 24-h transpiration water loss decreased. A correlation was established between leaf area and accumulation of malate. Water loss at early stages of leaf expansion may be connected with the shift to CAM and the water economy of the whole plant.     

Distinct feeding strategies of generalist and specialist spiders

1. Feeding behaviour of generalist and specialist predators is determined by a variety of trophic adaptations. Specialised prey‐capture adaptations allow specialists to catch relatively large prey on a regular basis. As a result, specialists might be adapted to exploit each item of prey more thoroughly than do generalists. 2. It was expected that obligatory specialist cursorial spiders would feed less frequently than generalists but for a longer time and, thus, that their foraging pause would be longer. First, the feeding frequencies of three generalist spider species (Cybaeodamus taim, Harpactea hombergi, Hersiliola sternbergsi) were compared with those three phylogenetically related specialist species: myrmecophagous Zodarion rubidum, and araneophagous Nops aff. variabilis and Palpimanus orientalis. 3. Generalists captured more prey, exploited each item of prey for a significantly shorter time, and had a shorter foraging pause than was the case for specialists. Generalists also gained significantly less relative amount of prey mass than did specialists. 4. Second, the study compared the prey DNA degradation rate in the gut of generalists and specialists by means of PCR. The degradation rate was not significantly different between specialists and generalists: the detectability half‐life was estimated to exist for 14.3 days after feeding. 5. This study shows that the feeding strategies of cursorial generalist and obligatory specialist spiders are different. Obligatory specialists have evolved a feeding strategy that is based on thorough exploitation of a few large prey, whereas generalists have evolved a strategy that is based on short exploitation of multiple small items of prey.